I think it is about a relationship full of emotions that is starting to cool down.
"My first day back in town"
[when I'm getting out of this rollercoaster of emotions and I'm starting to be myself again]
"The clouds up above they were hummin' our song"
[but stepping back brings memories from when they were starting and he couldn't get her out of his mind. This is where Intruder's comment comes in. He used to dream about her and have her in his mind all the time when they were starting (which was okay), but now he's afraid to relive all this feelings when he's trying to step back and start dreaming about her again]
I think it is about a relationship full of emotions that is starting to cool down.
"My first day back in town" [when I'm getting out of this rollercoaster of emotions and I'm starting to be myself again]
"The clouds up above they were hummin' our song" [but stepping back brings memories from when they were starting and he couldn't get her out of his mind. This is where Intruder's comment comes in. He used to dream about her and have her in his mind all the time when they were starting (which was okay), but now he's afraid to relive all this feelings when he's trying to step back and start dreaming about her again]